Euastacus armatus has been assessed as Data Deficient. This species has been previously listed as Vulnerable (A1ade) (Crandall 1996). The 8% decline in area of occupancy (AOO) documented by Gilligan et al. (2007) does not satisfy criterion A of the IUCN Categories and Criteria, which requires more than 30% population reduction measured over the longer of 10 years or three generations. Furthermore, their absence in that area has apparently not been confirmed (Gilligan et al. 2007). There does not appear to be any quantified data to satisfy any other criteria for listing in an IUCN threatened category. While this species is one of the better understood in the genus Euastacus, and is facing numerous threats, there is a paucity of appropriate data on this species distribution and abundance. More information is required, and it is acknowledged here that results of future research will probably show that a threatened classification is appropriate for this species.

The transfer of category from Vulnerable (VU) to DD reflects a revision of IUCN Categories and Criteria. Specifically, there appears to be no data supporting a more than 30% decline in any of the parameters listed for criterion A. Importantly, the change of category from VU to DD should not be interpreted as an improvement in the conservation status of the species. Conversely, this species may well be experiencing continued declines and facing threat of extinction. Its listing as DD highlights that there are specific research gaps that need to be addressed before its status can be determined. This research needs to be conducted across its entire range.

This species is endemic to Australia and is recognised as the second largest species of crayfish in the world (Van Praagh 2003). The species is found from near sea-level to over 700 m above sea level, and its distribution extends into New South Wales, South Australia, Victoria, and the Australian Capital Territory. The species range covers a distance north to south of 450 km, and a distance east to west of 800 km, rendering it the most widespread species in the genus (Morgan 1997). This species extent of occurrence (EOO) was estimated to exceed 150,000 km2 (J. Coughran and J.M. Furse pers. comm. 2008).

This distribution includes waterways in the Murrumbidgee, Murray, Mitta Mitta, Kiewa, Ovens and Goulburn River catchments. Although there were still commercial catches of this species reported in the Murray River in South Australia until the 1960s, this species is now considered rare or absent from this area downstream of Mildura in New South Wales (approximately 1,000 km of river) (Van Praagh 2003, Gilligan et al. 2007). Absence from this part of the river appears to be the most appreciable documented reduction in the distribution, estimated to be around 10% of its natural distribution (Gilligan et al. 2007). However, there has been no recent targeted sampling for this species in the South Australian reaches of the Murray River to confirm their continued absence (Gilligan et al. 2007).

Countries occurrence:

Native:

Australia (Australian Capital Territory, New South Wales, South Australia, Victoria)

The species is considered extinct or very rare in several of the lowland reaches of the rivers it inhabits (Gilligan et al. 2007). Subpopulations of this species have been identified as declining due largely to exploitation, inappropriate management of waterways (resulting in habitat degradation) and pollution (Gilligan et al. 2007). Since the 1940s, this crayfish species has also been steadily declining in the Murrumbidgee (particularly in the lower reaches) and Murray Rivers. However, this information is based solely on recreational fisher reports, as no primary data has thus far been collected to support these claims (N. Alves pers. comm. 2008). Recently there is some evidence of continued decline in the lower Murray River (McCarthy 2005).

Euastacus armatus occupies a range of habitats from small upland streams to large lowland rivers. The average size of individuals increases with the amount of habitat available. Important habitat characteristics include flowing water, clay banks, woody debris, deep holes, and boulders as these provide shelter (Gilligan et al. 2007). This species is tolerant of temperatures up to 27°C and moderate salinities (<16 parts per thousand), but is intolerant of low dissolved oxygen concentrations (Gilligan et al. 2007).

This species is a k strategist, meaning it is long lived when not disturbed and slow to reach maturity. The size of this species at sexual maturity varies widely between locations, and its age at sexual maturity may also vary (S. Lawler pers. comm. 2008).

The slow growth rate and low fecundity of many Euastacus speciesrenders them less resilient to reduction in population numbers through habitat destruction and catastrophic events (Van Praagh 2003).

This species is thought to have been affected by a number of threat processes, including habitat modification, pollution and pesticides, exploitation (i.e. recreational fishing) and the effects of introduced species (Van Praagh 2003, Gilligan et al. 2007).

The construction of weirs and resulting river regulation and seasonal flow reversal, and the widespread use of agrochemicals in the 1940s and 50s are likely to be the two primary threatening processes responsible for the decline in the range and abundance of this species, mainly through perturbation of breeding cycles and the timing of the release of young (S. Lawler pers. comm. 2008). Furthermore, the avoidance of weir pool environments in this species has been reported (Gilligan et al. 2007).

Agrochemicals, and even cow dung in the river water, have an impact on the abundance and health of this species symbionts (Temnocephalans) but the role they play in the health of the crayfish remains unknown (S. Lawler pers. comm. 2008).

Recreational fishing (in particular the taking of large adults) has the capacity to lead to serious and far reaching impacts on population structure (i.e. the stunted population phenomenon (Huner and Lindqvist 1985, Tulonen et al. 2008)), including impairment of reproductive success in females (Tulonen et al. 2008). Barker (1992) reported considerable variation in catch rates and sizes across different sites for this species.

Although widespread and less specific in its habitat requirements than most Euastacus species, it will potentially be impacted upon by the effects of climate change, as are other species in the genus Euastacus. A predicted drier climate will lead to decreased run-off, soil moisture and decreased environmental flows: particularly in areas of increasing demand for agricultural water supplies (Chiew and McMahon 2002, Howden 2003, Hughes, 2003, Pittock 2003, Hennessy 2006, Westoby and Burgman 2006, IPCC 2007).

This species is most threatened in the lower Murray River, where the extinction boundary seems to be moving east from Mildura (S. Lawler pers. comm. 2008).

In particular, given that the species occurs in the heavily degraded Murray-Darling system, it is conceivable that population declines will continue into the future, therefore, continued monitoring of the species and threats is required (J. Furse and J. Coughran pers. comm. 2009).

This species is listed as a threatened species across much of its range. It is protected in South Australia, listed as vulnerable in the Australian Capital Territory and threatened in Victoria. In New South Wales (NSW), this species occurs in the "Lower Murray River Endangered Ecological Community" and so is normally given the status of a threatened species across a large proportion of its range. Despite this, recreational fishing is permitted within the Endangered Ecological Community boundaries (Gilligan et al. 2007). Nationally, the conservation status was “indeterminate” due to a lack of knowledge at the time of the scoping report by Gilligan et al. (2007).

Fishing for this species is prohibited in the Australian Capital Territory and South Australia (PIRSA 2008, TAMS 2007).

In New South Wales, a minimum recreational size limit of 90 mm Orbital Carapace Length (OCL) is in place for any spiny crayfish (NSW DPI 2007). Only four of the more than 35 Euastacus species in NSW attain that size (Euastacus sulcatus, Euastacus spinifer, Euastacus valentulus and Euastacus armatus), so the regulation may in fact increase fishing pressure on these four species.

The spiny crayfish fishery was closed in Victoria from 1983 until 1991 (Barker 1992), but the current fishery for spiny crayfish is managed through a minimum size limit of 90 mm OCL, closed seasons and areas, and a bag limit of five per person per day (only one of which can exceed 120mm OCL) (DPI 2007).

Any future conservation measures or efforts for this species as a whole (i.e. throughout its range) are likely to be complicated, disjointed or hindered by the fact the species is distributed over three states and one territory, all of which have differing legislation and regulations regarding this species (J.M. Furse and J. Coughran pers. comm. 2008). Ideally a holistic and collaborative approach including all stakeholders (i.e. all relevant states and territories) should be adopted in any future research or conservation efforts for this species in order to maximize research outputs, conservation outcomes, and minimise duplication of effort, and thus domestic outlays.

The known and potential threats facing this species need to be more thoroughly investigated, documented, and monitored over time, as do subpopulations of this species. A systematic and thorough investigation of the species' contemporary distribution, and quantification of the population status (including any declines) is recommended urgently, as such data is essential for objective assessment against IUCN Categories and Criteria.

Monitoring of this species is essential to guarantee its survival. Despite the awareness of the species through angling, little is known of its ecology and threats (S. Lawler pers. comm. 2008).